1. Technical Field
This disclosure relates to crankshaft rotating angle controlling methods and crankshaft rotating angle controlling systems, and, more particularly, to a crankshaft rotating angle controlling method and a crankshaft rotating angle controlling system that reduce an engine starting torque of an integrated starter generator.
2. Description of Related Art
When an integrated starter generator (ISG) that uses a permanent magnetism design is applied to an idling turning off function, a speed of an engine from a rest state to an ignition state cannot be accomplished unless a torque is great enough. In particular, when the engine stops and a piston is just located around a top-dead-center of a compression stroke, an even greater starting torque is needed for starting the engine the next time. Therefore, the ISG has to drive a crankshaft of the engine to exceed the starting torque of the top-dead-center of the compression stroke, in order to start the engine and ensure that the speed is high enough for an ignition process to be performed successfully. In order to generate this great starting torque, the engine will suffer from a great torque for a long time. Therefore, the ISG has to be designed to have a large torsional moment, and comprise additional magnets and power components. A battery also has to provide a great current, which consumes power, and affects the life of the battery.
In order to ensure that the engine has a great torque to overcome the starting torque problem, an engine with a reduced compression device is brought to the market. The engine, when stopped, reverses a crankshaft to deduce the torque. When the engine is turned off and stops completely, a motor is controlled to drive the crankshaft of the engine to reverse, until the engine stops at a non-compression stroke. Therefore, when the engine closed the next time, a piston, before arriving the compression stroke, can be accelerated sufficiently to obtain great enough an inertia force. Such an inertia force, if combined with the driving torque of the engine, will exceed the starting torque, such that the piston can exceed the compression stroke.
However, the above techniques do not drive the motor to change the position of the crankshaft until the engine stops. As a result, additional energy is consumed. Since the motor is not driven until the engine stops, the motor will still vibrate suddenly, which make users uncomfortable.
Therefore, how to provide a crankshaft rotating angle controlling method and a crankshaft rotating angle controlling system that can reduce an engine starting torque is becoming an important issue in the art.